title: Quantitative proteomics reveals regulatory differences in the chondrocyte secretome from human medial and lateral femoral condyles in osteoarthritic patients.
abstract: BACKGROUND
  Osteoarthritis (OA) is a destructive joint disease and there are no known biomarkers available for an early diagnosis. To identify potential disease biomarkers and gain further insight into the disease mechanisms of OA we applied quantitative proteomics with SILAC technology on the secretomes from chondrocytes of OA knees, designated as high Mankin (HM) scored secretome. A quantitative comparison was made between the secretomes of the medial and lateral femur condyle chondrocytes in the same knee since the medial femur condyle is usually more affected in OA than the lateral condyle, which was confirmed by Mankin scoring. The medial/lateral comparison was also made on the secretomes from chondrocytes taken from one individual with no clinically apparent joint-disease, designated as low Mankin (LM) scored secretome.
  
  
  RESULTS
  We identified 825 proteins in the HM secretome and 69 of these showed differential expression when comparing the medial and lateral femoral compartment. The LM scored femoral condyle showed early signs of OA in the medial compartment as assessed by Mankin score. We here report the identification and relative quantification of several proteins of interest for the OA disease mechanism e.g. CYTL1, DMD and STAB1 together with putative early disease markers e.g. TIMP1, PPP2CA and B2M.
  
  
  CONCLUSIONS
  The present study reveals differences in protein abundance between medial/lateral femur condyles in OA patients. These regulatory differences expand the knowledge regarding OA disease markers and mechanisms.
authors.affiliation: Department of Clinical Chemistry and Transfusion Medicine, Institute of Biomedicine, Sahlgrenska Academy at the Sahlgrenska University Hospital, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Johan
authors.initials: J
authors.lastname: Stenberg
authors.affiliation: Department of Clinical Chemistry and Transfusion Medicine, Institute of Biomedicine, Sahlgrenska Academy at the Sahlgrenska University Hospital, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Ulla
authors.initials: U
authors.lastname: Rüetschi
authors.affiliation: Department of Biomedical Sciences and Veterinary Public Health, Division of Pathology, Pharmacology and Toxicology, Box 7028, SLUS-75007 Uppsala, Sweden.
authors.forename: Eva
authors.initials: E
authors.lastname: Skiöldebrand
authors.affiliation: Institute of Clinical Sciences, Department of Orthopaedic Surgery, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Johan
authors.initials: J
authors.lastname: Kärrholm
authors.affiliation: Department of Clinical Chemistry and Transfusion Medicine, Institute of Biomedicine, Sahlgrenska Academy at the Sahlgrenska University Hospital, University of Gothenburg, Gothenburg, Sweden.|Clinical Chemistry at Sahlgrenska University Hospital, Bruna Stråket 16, SE-41345 Gothenburg, Sweden.
authors.forename: Anders
authors.initials: A
authors.lastname: Lindahl